Summary

David Corenswet consumed 6,000 calories a day to transform into Superman, gaining 40lbs with intense workouts and a strict diet.
Trainer Paolo Mascitti emphasizes mastering classic exercises over flashy moves to build Corenswet’s superhero physique.
Mascitti praises James Gunn’s casting of Corenswet, declaring him the perfect Superman.

Following the release of our first look at David Corenswet as Superman in James Gunn’s DCU, Los Angeles-based trainer Paolo Mascitti also revealed our first look at the actor’s efforts to become a true Man of Steel. After sharing an image of the actor in the gym, Mascitti has now revealed what it took to get Corenswet into superhero shape (via GQ), with the Pearl star consuming up to 6,000 calories a day in order to put on the mass necessary to fill the iconic costume.

“This is a James Gunn film, and he has a specific vision of the entire project. David had been working out intensively before I met him, but he’s naturally a very lean guy. He’s 6’4” but we wanted to put more bulk on him. He probably went from 200lbs to 240lbs, but some of that mass will be shed as he continues to tone up.”

Mascitti has worked on a James Gunn project before, sculpting actor and comedian Flula Borg for his role in The Suicide Squad. Corenswet’s training began five months before production on Superman started, with the actor now “only fitting in three or four sessions a week” but still “working out for two hours a day,” Mascitti explains. Utilizing a classic push day, pull day, and legs day split, and exercises such as “presses, pull ups, pull downs, rows – all the big ones,” Mascitti explained that, to create a new Superman, he stuck with “what works.”

“This is just what works. A lot of trainers online are looking for the next best thing, but it’s not about showy moves, it’s about mastering the exercise and focusing on things like full range of motion, mastering the negative, stretching, and trying to progress in weight and reps.”

David Corenswet Is Superman, Trainer Paolo Mascitti Declares

As well as revealing how Corenswet got into Superman shape, Mascitti went onto heap praise on Gunn and his affinity for casting, declaring that Corenswet “is Superman.” Which he says is reflected in his good-nature, playfulness, “realistic expectation of himself and the role,” and his love of cereal…

“He is Superman. James Gunn is amazing at casting people, and this guy was born to be Superman. Ask any cast or crew member, David is the nicest guy, and I think, the perfect Superman.
He was on around 6,000 calories a day and his diet was strict, but not as strict as I would have liked,” laughs Mascitti. “Half of his training had to be done over FaceTime and half in person as he wasn’t in Los Angeles all the time. We’d speak remotely and I’d ask him about his diet and he’d be eating cereal! He’d ask What’s wrong with cereal!? But that’s why he’s the perfect Superman, he has a realistic expectation of himself and the role.”

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Not only is Corenswet just like Superman, but his co-star Nicholas Hoult also has a bit of Lex Luthor about him, with Mascitti revealing that there was a healthy rivalry between the two in the gym.

“Nick is so easy going apart from when it comes to working out. He pushes himself and pushes himself. When I first met him I said Oh my God, this guy can do absolutely everything. I will throw weights at him, cardio, he smashes it all, he loves it all.”

Written and directed by James Gunn and starring David Corenswet as Clark Kent/Superman and Rachel Brosnahan as Lois Lane,
Superman
will be released in theaters on July 11, 2025.